1. Field of the Invention
The invention relates generally to electronic communication and home automation, and more particularly, to devices for communicating on home-appliance networks.
2. Description of the Related Art
Home automation systems have gained increasing popularity due to advances in digital signal processing and reductions in the cost of home computer equipment. These systems allow centralized and remote control over electric and electronic appliances and devices in the home, such as interior lights, exterior lights, fans, and other devices. One system, by X10 Ltd., uses electrical sockets and electrical switches with transceivers that communicate over a house's electrical wiring system. The sockets and switches can receive commands from and/or provide status information to one or more control stations plugged into the house's wiring. The control system may be a specialized unit or a home computer configured to interface with the house wiring. With the appliances connected through this system, a user can readily execute simple controls over the appliances from a central location. These controls include turning on and off lights, dimming lights, setting lights and stereo equipment to turn on or off at predetermined or random times, and other similar functions.
The appliances in these systems communicate through high-frequency pulses (typically 120 kHz) transmitted on the home wiring grid during the zero-crossings of the 120 VAC/60 Hz voltage cycles. The presence or absence of a high-frequency pulse indicates a binary 1 or 0. The information is communicated with some redundancy: the two zero-crossings in each 60 Hz cycle are used to transmit one bit. If the high-frequency pulse is present during the first zero-crossing, it will be absent during the second, and vice-versa. In this version of the signaling system, the appliances can thus communicate at a rate of up to 60 bits per second.
With increasing complexity of appliances in the home, it is expected that more sophisticated signaling techniques will be necessary for transmitting information among the connected appliances. It may be useful, for example, to have increased data rates, enhanced noise immunity, simultaneous communication with more than one device, or the ability to communicate on a network other than the home wiring grid. Similarly, the prior art might require each device to have a complex input stack for monitoring all of the commands over the network instead of just the commands relevant to that particular device. Since implementing this stack would increase the software complexity, more hardware and computing power would also be required to support it. As a result, it might also be desirable to simplify these software and hardware requirements.